Linear frac pump assembly

ABSTRACT

A linear frac pump includes a fluid end having an inlet valve disposed proximate to an inlet port, and a discharge valve disposed proximate to a discharge port. The pump further includes a first plunger rod housed within a first plunger housing, the first plunger rod having first and second ends, the first end being in fluid communication with the fluid end, and the second end being coupled to a first actuator. The pump includes a second plunger rod housed within a plunger housing, the second plunger rod having first and second ends, the first end being in fluid communication with the fluid end, and the second end being coupled to a second actuator. The first and second plunger rods and housings are coupled to the fluid end and the first and second plunger rods operate in sync to drive fluids inward from the inlet port and outward via the discharge port being regulated by the inlet and discharge valves.

FIELD

The present disclosure relates to positive displacement pumps, and inparticular, to a linear frac pump assembly with a folded configuration.

BACKGROUND

Large powerful pumps are commonly used for mining and oilfieldapplications, such as, for example, hydraulic fracturing. Duringhydraulic fracturing, fracturing fluid (i.e., cement, mud, frac sand andother material) is pumped at high pressures into a wellbore to cause theproducing formation to fracture. One commonly used pump in hydraulicfracturing is a high-pressure reciprocating pump, like the SPM® Destiny™TWS 2500 frac pump or the SPM® QEM 3000 Continuous Duty Frac Pump,manufactured by S.P.M. Oil & Gas, a Caterpillar Company located in FortWorth, Tex. In operation, the fracturing fluid is caused to flow intoand out of a pump fluid chamber as a consequence of the reciprocation ofa piston-like plunger respectively moving away from and toward the fluidchamber. As the plunger moves away from the fluid chamber, the pressureinside the chamber decreases, creating a differential pressure across aninlet valve, drawing the fracturing fluid through the inlet valve intothe chamber. When the plunger changes direction and begins to movetowards the fluid chamber, the pressure inside the chamber substantiallyincreases closing the inlet valve increasing the differential pressureacross an outlet valve and causes the outlet valve to open, enabling thehighly pressurized fracturing fluid to discharge through the outletvalve into the wellbore.

A typical frac unit is powered with a diesel engine driving a frac pumpthrough a multispeed transmission. The rotational energy transferred tothe reciprocating frac pump is channeled to horizontal plunger bores forpumping via crankshafts and connector rods. The operating conditions areoften extreme involving high fluid flow and high operating pressures(oftentimes up to 15,000 psi). Pressure fluctuations as seen in dieselpowered units or other internal combustion-based units often causeundesirable cyclic stresses on components, shortening their lives.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an embodiment of a linear pump accordingto the teachings of the present disclosure;

FIG. 2 is a cross-sectional view of an embodiment of a linear pumpaccording to the teachings of the present disclosure;

FIG. 3 is a schematic cross-sectional view of an embodiment of thelinear pump according to the teachings of the present disclosure; and

FIG. 4 is a schematic cross-sectional view of an embodiment of a linearpump having a folded configuration according to the teachings of thepresent disclosure.

DETAILED DESCRIPTION

The introduction of natural gas as “free fuel” for frac operations hasled to investigation of the best way to utilize natural gas to generatepumping power. One option is to use a large gas turbine generator thatcreates electrical power to run the frac job on electricity. Sinceelectric drive is not limited to the maximum diesel engine powerfeasible for a mobile frac unit, a larger pump is possible. The abilityto deploy larger pumps would lead to fewer units required on a fracsite. Fewer units on location translates to a lower total cost ofownership and operating cost.

Reciprocating pumps have many moving parts and so do the power systemsthat drive them. Replacing reciprocating pumps and their associateddrive systems with a linear pump that is actuated electrically through aplanetary thread drive provides many advantages. The linear pumpingaction is created by the movement of the screw through theelectrically-powered planetary drive.

In a first embodiment of a linear pump (described in a co-pending PCTApplication No. WO2017/139583), a linearly actuated double-action pumpincludes a centrally-disposed drive system coupled to two fluid ends ateither end along the linear axis, where the drive system drives theplunger rod to move the fluid in both fluid ends. In an exampleembodiment, an electric linear pump may use a planetary screw drive(e.g., planetary gears surrounding a threaded rod to convert rotationalmotion of the planetary gears to the linear translation movement of thethreaded rod) to linearly move (i.e., translate) plunger rods instead ofthe traditional diesel engines. The threaded rod coupled to the drivesystem has plunger sections on both ends such that when the plunger rodmoves in either direction, one of the two ends will be pumping outfluids while the other drawing in fluids. In other embodiments, theelectric actuator may be in the form of a winding that uses electriccurrent to create a magnetic field to move the rod along its axis (e.g.,similar to solenoid actuation). A fluid end is coupled with each of thetwo plunger ends to control fluid charging on the suction stroke andpressure discharge on the power stroke. The electricity supplied to theplanetary thread drive may be provided from the grid or produced by anonsite generator using local natural gas, thus minimizing fuel costs.

In a second embodiment of the linear actuated pump 10 shown in FIGS. 1-3, a centrally-disposed fluid end 12 is coupled to two actuators 14 and15 on its two sides along a linear axis. The actuators 14 and 15 may behydraulic or electro-mechanic actuators that are in fluid communicationwith a hydraulic/electrical-controlled drive system (not shown) that mayincorporate a planetary screw drive or a solenoid drive system. Theactuators 14 and 15 each drives or causes linear displacement ofrespective plungers 16 and 17 that reciprocate within their respectivefluid bores defined within respective plunger housings 18 and 19. Inthis configuration, the stroke length of each plunger rod 16 and 17 canbe halved and a smaller screw drive system may be employed and stillachieve the same horsepower and fluid rate output when compared to theabove-referenced double-action pump configuration. In this more compactsecond configuration, the overall length of the pump assembly 10 isreduced by the size of one fluid end. Further, because of the shorterstroke length, it is easier to achieve and maintain accurate alignmentof the fluid end and hydraulic drive components. Within the fluid end 12are an inlet and discharge valves 22 and 23 that regulate the intake anddischarge of fluids from the pump through inlet and discharge ports (notexplicitly shown). The inlet port is connected to a manifold (not shown)that supplies the frac fluid and the discharge port is connected to adischarge line (not shown) that leads to a wellbore. According to anembodiment, multiple linear pumps can be fluidly coupled at thedischarge lines to deliver a constant high-pressure flow to thewellhead.

In a third embodiment as shown in FIG. 4 , the “legs” of a linear pumpassembly 40, including the respective actuators 44 and 45, plungerpistons 46 and 47, and piston housings 48 and 49, are “folded” at thecentrally-disposed fluid end 42 so that the “legs” become disposedproximate to and alongside each other. Same as before, the actuators 44and 45 may be hydraulic or electro-mechanic actuators that are in fluidcommunication with a hydraulic/electrical-controlled drive system thatincorporates a planetary screw drive or a solenoid drive system. In this“folded” configuration, the overall length of the linear pump assembly40 is greatly reduced to about half of the embodiment shown in FIG. 3 .The great reduction in overall length enables more flexibility withrespect to the arrangement of multiple pump assemblies within a limitedfootprint, such as on a trailer bed that is typically 48 feet in lengthand up to 8 feet in width.

The linear pump assemblies described herein may operate under or with acontrol module (not explicitly shown) that include a computer withassociated software installed therein, to cooperatively operate thedrive system and hydraulic/electrical-mechanical actuators so that thefluid output from the fluid end is smooth with minimized fluidpulsation. A number of sensors may be used to measure and monitor avariety of pump operating characteristics that are provided as input tothe control module. The monitored pump characteristics may include, forexample, fluid pressures, fluid flow rate, motor speed, etc.

In some embodiments, multiple pump assemblies, such as from two to sixunits, may be used for redundancy and configured to maintain a constantor steady output flow (i.e., smooth output). In differentimplementations, different plunger sizes and fluid end sizes (e.g.,different product families) may be provided for a range of pressuresneeded for different applications.

In some examples, the motor used in the linear electric pump may be apermanent magnet synchronous motor. The bearing may be a spherical axialthrust bearing. The planetary gears may be directly driving a threadedplunger rod without additional transmission assemblies. In some cases,the electric linear pump may have one or more sensors to measure therotary position of the plunger rod or the planetary gears to determineposition, speed, or other information of the plunger rod. The motor,gears or planetary gears, bearings, and the threaded rods may beenclosed within a housing for lubrication and cooling purposes. Coolingsystem is provided for both the electric motor and the driven gearsthereof. A logic control unit (LCU) may be used to accurately controlthe rotation of the motors and provide control according to controlsignals per control algorithm or programs. Detailed examples areprovided below. One benefit of the electric motor-driven linear pumpsdescribed herein is much reduced noise generation than traditionaloperations using diesel engines and power ends.

The features of the present invention which are believed to be novel areset forth below with particularity in the appended claims. However,modifications, variations, and changes to the linear pump configurationsdescribed above will be apparent to those skilled in the art, and thelinear actuated pump configuration described herein thus encompassessuch modifications, variations, and changes and are not limited to thespecific embodiments described herein.

What is claimed is:
 1. A linear frac pump assembly comprising: a fluidend; a first plunger rod having first and second ends, the first endbeing in fluid communication with the fluid end, and the second endbeing coupled to a first actuator, the first plunger rod being housedwithin a first plunger housing defining a first plunger bore, the firstplunger rod being configured for linear reciprocation within the firstplunger bore driven by the first actuator; a second plunger rod havingfirst and second ends, the first end thereof being in fluidcommunication with the fluid end, and the second end being coupled to asecond actuator, the second plunger rod being housed within a secondplunger housing defining a second plunger bore, the second plunger rodbeing configured for linear reciprocation within the second plunger boredriven by the second actuator; and the first and second plunger boresbeing in in fluid communication with the fluid end and further beinglinear alignment with one another.
 2. The linear frac pump assembly ofclaim 1, wherein at least one of the first and second actuator comprisesan electric motor.
 3. The linear frac pump assembly of claim 1, whereinat least one of the first and second actuator comprises an electricmotor configured to engage the respect at least one of the first andsecond plunger rod.
 4. The linear frac pump assembly of claim 3, whereinone or more gears of the electric motor are driven by a planetary geartransmission receiving rotation input from an electrically poweredrotor.
 5. The linear frac pump assembly of claim 1, wherein the fluidend comprises an inlet valve disposed proximate to an inlet port, and adischarge valve disposed proximate to a discharge port.
 6. The linearfrac pump assembly of claim 1, wherein the first and second actuatorsare selected from the group consisting of hydraulic andelectro-mechanical actuators.
 7. A linear pump assembly comprising: afluid end; a first plunger rod housed within a first plunger housingcoupled to the fluid end, the first plunger rod having first and secondends, the first end being in fluid communication with the fluid end, andthe second end being coupled to a first actuator; and a second plungerrod housed within a plunger housing coupled to the fluid end, the secondplunger rod having first and second ends, the first end being in fluidcommunication with the fluid end, and the second end being coupled to asecond actuator, the first and second plunger rods and housing inparallel alignment and alongside one another and are traveling in thesame direction and in sync.
 8. The linear frac pump assembly of claim 7,wherein the first and second actuators are selected from the groupconsisting of hydraulic and electro-mechanical actuators.
 9. The linearpump assembly of claim 7, wherein at least one of the first and secondactuator comprises an electric motor.
 10. The linear pump assembly ofclaim 7, wherein at least one of the first and second actuator comprisesan electric motor configured to engage the respect at least one of thefirst and second plunger rod.
 11. The linear pump assembly of claim 9,wherein one or more gears of the electric motor are driven by aplanetary gear transmission receiving rotation input from anelectrically powered rotor.
 12. The linear frac pump assembly of claim7, wherein the fluid end comprises an inlet valve disposed proximate toan inlet port, and a discharge valve disposed proximate to a dischargeport.
 13. A linear pump assembly comprising: a fluid end having an inletvalve disposed proximate to an inlet port, and a discharge valvedisposed proximate to a discharge port; a first plunger rod housedwithin a first plunger housing, the first plunger rod having first andsecond ends, the first end being in fluid communication with the fluidend, and the second end being coupled to a first actuator; and a secondplunger rod housed within a plunger housing, the second plunger rodhaving first and second ends, the first end being in fluid communicationwith the fluid end, and the second end being coupled to a secondactuator, the first and second plunger rods and housings being coupledto the fluid end and the first and second plunger rods operate in syncto drive fluids inward from the inlet port and outward via the dischargeport being regulated by the inlet and discharge valves.
 14. The linearpump assembly of claim 13, wherein the first and second plunger housingsare in linear alignment.
 15. The linear pump assembly of claim 13,wherein the first and second plunger housings are parallel and disposedalongside one another.
 16. The linear pump assembly of claim 13, whereinat least one of the first and second actuator comprises an electricmotor.
 17. The linear pump assembly of claim 13, wherein at least one ofthe first and second actuator comprises an electric motor configured toengage the respect at least one of the first and second plunger rod. 18.The linear pump assembly of claim 17, wherein one or more gears of theelectric motor are driven by a planetary gear transmission receivingrotation input from an electrically powered rotor.
 19. The linear pumpassembly of claim 13, wherein at least one of the first and secondactuator comprises an electric motor.